Need some help w/ easy power

I have a 2001 s4, I don't know much about to many performance upgrade beside the the obvious. chips, intakes, exhaust, turbos....

what are some smaller things i can do to make the car run better, or things that are known to go wrong that usually affect the cars performance. e.x. I read that the throttlebody boot goes bad and it could affect the boost..therefore the performance.....what other stuff could go wrong to cause performance losses, that may need fixed.....I don't have any problems now but, i want to catch them before they happen.

any input on known or expirienced problems would help and be greatly appriciated....also any input on smaller performance parts would be great too.... i'm going to work up to the bigger stuff closer to spring, but i want to take car of the smaller stuff during the winter.

thanks